Transmitting device for high speed communication, interface circuit and system including the same

ABSTRACT

A transmission device may include a main driver configured to drive an output node based on an input signal, and may generate an output signal with multiple levels. The transmission device may include a variable emphasis driver configured to drive the output node with various driving forces based on transition information of the input signal.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119(a) toKorean application number 10-2015-0050940, filed on Apr. 10, 2015, inthe Korean Intellectual Property Office, which is incorporated herein byreference in its entirety.

BACKGROUND

1. Technical Field

Various embodiments generally relate to a communication system, and moreparticularly, to a transmitting device for high speed communication, aninterface circuit and a system including the same.

2. Related Art

Electronic products for personal uses, such as a personal computer, atablet PC, a laptop computer and a smart phone, are constructed byvarious electronic components. Two different electronic components inthe electronic products may communicate at a high speed to process alarge amount of data within a short amount of time. The electroniccomponents generally communicate through interface circuits. Theelectronic components communicate in various schemes. As an example, oneof the schemes may be a serial communication scheme.

As the performances of electronic components are improved, necessity fora communication scheme capable of increasing a bandwidth and reducingpower consumption is being increased. In order to meet such necessity,various new serial communication schemes are suggested in the art, andimproved interface circuits for supporting the new serial communicationschemes are being developed.

SUMMARY

In an embodiment, a transmission device may be provided. Thetransmission device may include a main driver. The main driver may beconfigured to drive an output node based on an input signal, and may beconfigured to generate an output signal with multiple levels. Thetransmission device may include a variable emphasis driver configured todrive the output node with various driving forces based on transitioninformation of the input signal.

In an embodiment, a transmission device may be provided. Thetransmission device may include a main driver configured to output anoutput signal with one level among a high level, a middle level and alow level, to an output node, based on an input signal. The transmissiondevice may include a variable emphasis driver configured to drive theoutput node with one of first and second driving forces based ontransition information of the input signal.

In an embodiment, a transmission device may be provided. Thetransmission device may include a variable emphasis driver configured tochange a pre-emphasis strength according to a level by which an inputsignal transitions to control a transition time of an output signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a representation of an example of theconfiguration of a system in accordance with an embodiment.

FIG. 2 is a diagram illustrating a representation of an example of theconfiguration of the interface circuit of the first device illustratedin FIG. 1.

FIG. 3 is a diagram illustrating a representation of an example of theconfiguration of the interface circuit of the second device illustratedin FIG. 1.

FIG. 4 is a diagram illustrating a representation of an example of asystem including electronic components configured to use the balancedcode multilevel signal transmission scheme described with reference toFIGS. 1 to 3.

FIG. 5 is a diagram illustrating a representation of an example of theconfiguration of a transmission device in accordance with an embodiment.

FIG. 6 is a diagram illustrating a representation of an example of theconfiguration of a transmission device in accordance with an embodiment.

FIG. 7 is a representation of an example of a timing diagram to assistin the explanation of the operation of the transmission deviceillustrated in FIG. 6.

DETAILED DESCRIPTION

Hereinafter, an interface circuit for high speed communication and asystem including the same will be described below with reference to theaccompanying drawings through various examples of embodiments.

Referring to FIG. 1, a system 1 in accordance with an embodiment mayinclude a first device 110 and a second device 120. The first device 110may represent a component configured to transmit data, and the seconddevice 120 may represent a component configured for receiving the datatransmitted from the first device 110. For example, the system 1 mayinclude a master device and a slave device. When data are transmittedfrom the master device to the slave device, the master device may be thefirst device 110, and the slave device may be the second device 120.Conversely, when data is transmitted from the slave device to the masterdevice, the master device may be the second device 120, and the slavedevice may be the first device 110.

The master device may be a host device such as a processor, and theprocessor may include, for example but not limited to, a centralprocessing unit (CPU), a graphic processing unit (GPU), a multimediaprocessor (MMP) or a digital signal processor (DSP). The master devicemay be realized in the form of a system-on-chip (SoC) by combiningprocessor chips having various functions, such as applicationprocessors. The slave device may be a memory, and the memory may includea volatile memory and/or a nonvolatile memory. The volatile memory mayinclude, for example but not limited to, an SRAM (static RAM), a DRAM(dynamic RAM) and an SDRAM (synchronous DRAM), and the nonvolatilememory may include, for example but not limited to, a ROM (read onlymemory), a PROM (programmable ROM), an EEPROM (electrically erasable andprogrammable ROM), an EPROM (electrically programmable ROM), a flashmemory, a PRAM (phase change RAM), an MRAM (magnetic RAM), an RRAM(resistive RAM) and an FRAM (ferroelectric RAM).

The first device 110 and the second device 120 may be electricallycoupled through at least one signal transmission line group, and form alink. The first device 110 and the second device 120 may communicate ina balanced code multilevel signal transmission scheme through the atleast one signal transmission line group. The at least one signaltransmission line group may include a plurality of signal transmissionlines. For example, in the example where the first device 110 and thesecond device 120 use an n level (phase or state) signal transmissionscheme, the number of signal transmission lines forming one signaltransmission line group may be equal to or larger than n. The firstdevice 110 and the second device 120 may be electrically coupled througha plurality of signal transmission line groups. In FIG. 1, the firstdevice 110 and the second device 120 may be electrically coupled throughfirst and second signal transmission line groups 131 and 132, and eachof the first and second signal transmission line groups 131 and 132 mayinclude at least n signal transmission lines.

The first device 110 and the second device 120 may respectively includeinterface circuits 111 and 121. The interface circuits 111 and 121 maybe physical layers for communication between the first device 110 andthe second device 120. The interface circuit 111 of the first device 110may convert a plurality of data into n level symbols, and may transmitthe n level symbols to the second device 120 through the signaltransmission line groups 131 and 132. The n level symbols may beconfigured by balanced codes. The interface circuit 121 of the seconddevice 120 may receive the n level symbols transmitted through thesignal transmission line groups 131 and 132, and may recover the n levelsymbols into the plurality of data. For instance, in the example wherethe plurality of data are m bits, the interface circuit 111 of the firstdevice 110 may convert the m bit data into a plurality of n levelsymbols, and may sequentially transmit in series the plurality of nlevel symbols through the signal transmission lines. The interfacecircuit 121 of the second device 120 may sequentially receive theplurality of n level symbols, and recover the m bit data based on theplurality of n level symbols. In the example where the first device 110and the second device 120 include a plurality of signal transmissionline groups, information corresponding to the number of signaltransmission line groups*n level symbols may be simultaneouslytransmitted.

In an embodiment, one of the n level symbols may not be configured by abalanced code, and the plurality of n level symbols may be configured bybalanced codes. That is to say, the plurality of n level symbols maybecome balanced codes in their entireties. Accordingly, even though eachsymbol is not configured by a balanced code, in the example where theplurality of n level symbols are transmitted through the signaltransmission line groups 131 and 132, balanced code multilevel signaltransmission may be implemented.

FIG. 2 is a diagram illustrating a representation of an example of theconfiguration of the interface circuit 111 of the first device 110illustrated in FIG. 1. Referring to FIG. 2, the interface circuit 111 ofthe first device 110 may include a mapper 210, a serialization unit 220,and a transmission driver 230. In FIG. 2, it is illustrated as anexample that the interface circuit 111 is disposed for a three levelserial communication scheme. Also, it is illustrated as an example thatthe interface circuit 111 is electrically coupled with the interfacecircuit 121 of the second device 120 through one signal transmissionline group, and the one signal transmission line group may include threesignal transmission lines 251, 252 and 253 to transmit three levelsymbols. The mapper 210 may convert data into symbols. For example, themapper 210 may convert 16 bit data DQ<0:15> into seven symbols. Eachsymbol may have three level information. The data DQ<0:15> may beinformation of a pattern suitable for being used in the first device 110and the second device 120. The mapper 210 may convert the data DQ<0:15>into symbols corresponding to the pattern of the data DQ<0:15> accordingto a table stored therein. For example, the mapper 210 may encode sevensymbols, each symbol having three level information. Three levels may bedefined as a high level, a middle level and a low level. For example,the high level may have a voltage level corresponding to 3/4 V, themiddle level may have a voltage level corresponding to 2/4 V, and thelow level may have a voltage level corresponding to 1/4 V. Since asystem using the multilevel signal transmission scheme such as thesystem 1 of FIG. 1 does not use a clock signal, the first device 110 andthe second device 120 may internally generate clock signals based on thesignals transmitted through the signal transmission line groups 131 and132.

The serialization unit 220 may receive the seven symbols, each symbolhaving the three level information, and sequentially output the sevensymbols, each symbol having the three level information. Thetransmission driver 230 may sequentially output the seven symbols, eachsymbol having the three level information, outputted from theserialization unit 220, to the signal transmission lines 251, 252 and253. The transmission driver 230 may include three transmitters TX, andthe three transmitters TX may respectively output one of three levelsymbols outputted from the serialization unit 220, to the signaltransmission lines 251, 252 and 253. The serialization unit 220 and thetransmission driver 230 may transmit in series seven symbols through thesignal transmission lines 251, 252 and 253.

FIG. 3 is a diagram illustrating a representation of an example of theconfiguration of the interface circuit 121 of the second device 120illustrated in FIG. 1. Referring to FIG. 3, the interface circuit 121 ofthe second device 120 may include a reception driver 310, a clock datarecovery CDR circuit 320, a parallelization unit 330, and a demapper340. The reception driver 310 may be electrically coupled with thesignal transmission lines 251, 252 and 253, and may receive the signalstransmitted from the first device 110. The reception driver 310 mayinclude three receivers RX. The three receivers RX are respectivelyelectrically coupled with the three signal transmission lines 251, 252and 253 configured for transmitting three level symbols. The clock datarecovery circuit 320 may receive the three level symbols received by thereception driver 310, and generate a clock signal CLK based on the threelevel symbols. The parallelization unit 330 may align the plurality ofthree level symbols received through the reception driver 310, andoutput the aligned symbols in synchronization with the clock signal CLK.The reception driver 310 and the parallelization unit 330 may receiveseven symbols, each symbol having three level information. The demapper340 decodes the seven symbols. The demapper 340 may decode the sevensymbols in a scheme corresponding to the encoding scheme of the mapper210. The demapper 340 may convert the seven symbols into 16 bit dataDQ<0:15> according to a table stored therein. The 16 bit data DQ<0:15>outputted by the demapper 340 of the interface circuit 121 may besubstantially the same data as the data inputted to the mapper 210 ofthe interface circuit 111.

FIG. 4 is a diagram illustrating a representation of an example of asystem 4 including electronic components configured to use the balancedcode multilevel signal transmission scheme described above withreference to FIGS. 1 to 3. Referring to FIG. 4, the system 4 may includea host device 410, a large capacity storage device 421, a memory 422,and a display device 423. The system 4 may include a camera device 424,a modem 425, and a bridge chip 426. The system 4 may include a wirelesschip 427, a sensor 428, and an audio device 429. The host device 410 maycommunicate with the remaining components by forming respectiveindividual links. The components for an electronic device illustrated inFIG. 4 are nothing but a mere illustration, and it is to be noted thatthe system 4 may include any components capable of performing datacommunication with the host device 410.

The host device 410 may include at least one integrated circuit devicesuch as an application processor and an application specific integratedcircuit (ASIC). The large capacity storage device 421 may include atleast one storage device such as a solid state drive (SSD) and a flashdrive through USB coupling. The memory 422 may include any kind(s) ofmemory devices. For example, the memory 422 may include a volatilememory device such as a DRAM (dynamic RAM), or may include a nonvolatilememory device such as a ROM (read only memory), a PROM (programmableROM), an EEPROM (electrically erasable and programmable ROM), an EPROM(electrically programmable ROM), a FLASH memory, a PRAM (phase changeRAM), an MRAM (magnetic RAM), an RRAM (resistive RAM) and an FRAM(ferroelectric RAM).

The host device 410 may communicate with the large capacity storagedevice 421 and the memory 422 by forming respective links. The hostdevice 410, the large capacity storage device 421 and the memory 422 mayinclude the interface circuits illustrated in FIGS. 1 to 3, and mayexchange signals with one another with a serial communication scheme.Similarly, the host device 410 may communicate serially with the displaydevice 423, the camera device 424, the modem 425, the bridge chip 426,the wireless chip 427, the sensor 428 and the audio device 429 byforming individual links.

FIG. 5 is a diagram illustrating a representation of an example of theconfiguration of a transmission device 5 in accordance with anembodiment. The transmission device 5 of FIG. 5 may be applied as thetransmission driver 230 of the interface circuit 111 of the first device110 illustrated in FIG. 2. Referring to FIG. 5, the transmission device5 may include a main driver 510, and a variable emphasis driver 520. Themain driver 510 may output an output signal OUT with multiple levels toan output node 530 based on an input signal IN. The multiple levels maybe at least 3 levels. The multiple levels may include a plurality oflevels respectively having a potential difference corresponding to aunit voltage.

In an embodiment, the multiple levels may be 3 levels, and may include ahigh level, a middle level and a low level. The high level may have apotential higher than the middle level, and the middle level may have apotential higher than the low level. The respective levels may have apotential difference corresponding to a unit voltage. The high level,the middle level and the low level may be levels between the powersupply voltage of the main driver 510 and a ground voltage. Forinstance, in the example where the level of the power supply voltage isV, the high level may be a voltage level corresponding to 3/4*V, themiddle level may be a voltage level corresponding to 2/4*V, and the lowlevel may be a voltage level corresponding to 1/4*V. In the examplewhere the input signal IN is a high level, the main driver 510 maygenerate the output signal OUT with the high level by driving the outputnode 530 to a voltage level corresponding to the high level. In theexample where the input signal IN is a low level, the main driver 510may generate the output signal OUT with the low level by driving theoutput node 530 to a voltage level corresponding to the low level. Inthe example where the input signal IN is a middle level, the main driver510 may generate the output signal OUT with the middle level by drivingthe output node 530 to a voltage level corresponding to the middlelevel.

The variable emphasis driver 520 may drive the output node 530 withvarious driving forces based on the transition information of the inputsignal IN. The variable emphasis driver 520 may change a strength fordriving the output node 530, according to a change in a voltage level bywhich transition occurs when the input signal IN transitions. Thevariable emphasis driver 520 may drive the output node 530 strongly asthe voltage level of the input signal IN changes largely. In otherwords, the variable emphasis driver 520 may increase a strength fordriving the output node 530, as a voltage level difference by which theinput signal IN transitions is large. The variable emphasis driver 520may drive the output node 530 with a predetermined strength, when theinput signal IN transitions from any one level to an adjacent level. Thevariable emphasis driver 520 may drive the output node 530 until thevoltage level of the output node 530 transitions from any one level toanother level.

The adjacent level may mean a level that is higher or lower by a unitvoltage than the any one level. The variable emphasis driver 520 maydrive the output node 530 with a strength larger than the predeterminedstrength, when the input signal IN transitions from the any one level toa level exceeding the adjacent level. The level exceeding the adjacentlevel may mean a level that is higher or lower by a potential exceedingthe unit voltage than the any one level.

For example, it is assumed that the multiple levels include 4 levels,the input signal IN currently inputted is the first level, and an inputsignal to be inputted next may transition to one of the second to fourthlevels having potentials higher sequentially by a unit voltage than thefirst level. The second level may correspond to a potential higher bythe unit voltage than the first level, the third level may correspond toa potential higher by the unit voltage than the second level, and thefourth level may correspond to a potential higher by the unit voltagethan the third level. In the example where the input signal INtransitions from the first level to the second level, the variableemphasis driver 520 may drive the output node 530 with the smallestdriving force. In the example where the input signal IN transitions fromthe first level to the fourth level, the variable emphasis driver 520may drive the output node 530 with the largest driving force. In theexample where the input signal IN transitions from the first level tothe third level, the variable emphasis driver 520 may drive the outputnode 530 with a driving force larger than the smallest driving force andsmaller than the largest driving force. Accordingly, the variableemphasis driver 520 efficiently enables the pre-emphasis of the outputsignal OUT according to a level change of the input signal IN.

The transmission device 5 may further include an output control unit540. The output control unit 540 may receive the input signal IN, andmay generate main driver control signals MCON<0:n> and variable emphasisdriver control signals PCON<0:m> based on the input signal IN. Theoutput control unit 540 may control the driving force of the main driver510 and the driving force of the variable emphasis driver 520 bygenerating the main driver control signals MCON<0:n> and the variableemphasis driver control signals PCON<0:m>.

FIG. 6 is a diagram illustrating a representation of an example of theconfiguration of a transmission device 6 in accordance with anembodiment. Referring to FIG. 6, the transmission device 6 may include aplurality of main drivers and a plurality of variable emphasis drivers.While FIG. 6 illustrates an example in which 3 main drivers and 3variable emphasis drivers are provided, it is to be noted that theembodiment is not limited to such an example. The number of main driversand variable emphasis drivers may be changed according to the number ofthe levels, phases or states of the data and/or symbols to betransmitted by the transmission device 6. A first main driver 601 and afirst variable emphasis driver 602 may be electrically coupled with afirst signal transmission line 611. The first signal transmission line611 may be electrically coupled with a pad and an output node, and maytransmit a first output signal DQ_A. The first main driver 601 and thefirst variable emphasis driver 602 may drive the first signaltransmission line 611 and transmit the first output signal DQ_A throughthe first signal transmission line 611. A second main driver 603 and asecond variable emphasis driver 604 may be electrically coupled with asecond signal transmission line 631. The second signal transmission line631 may be electrically coupled with a pad and an output node, and maytransmit a second output signal DQ_B. The second main driver 603 and thesecond variable emphasis driver 604 may drive the second signaltransmission line 631 and transmit the second output signal DQ_B throughthe second signal transmission line 631. A third main driver 605 and athird variable emphasis driver 606 may be electrically coupled with athird signal transmission line 651. The third signal transmission line651 may be electrically coupled with a pad and an output node, and maytransmit a third output signal DQ_C. The third main driver 605 and thethird variable emphasis driver 606 may drive the third signaltransmission line 651 and may transmit the third output signal DQ_Cthrough the third signal transmission line 651.

The first to third main drivers 601, 603 and 605 may respectivelygenerate the first to third output signals DQ_A, DQ_B and DQ_C withmultiple levels based on input signals DQ<0:2>. For example, if thefirst input signal DQ<0> is a high level, the second input signal DQ<1>is a middle level and the third input signal DQ<2> is a low level, thefirst main driver 601 may drive the first signal transmission line 611to the high level, the second main driver 603 may drive the secondsignal transmission line 631 to the middle level, and the third maindriver 605 may drive the third signal transmission line 651 to the lowlevel. The first to third main drivers 601, 603 and 605 may operate byreceiving a power supply voltage. For instance, in the example where thelevel of the power supply voltage is V, the high level may be a voltagelevel corresponding to 3/4*V, the middle level may be a voltage levelcorresponding to 2/4*V, and the low level may be a voltage levelcorresponding to 1/4*V.

The first to third variable emphasis drivers 602, 604 and 606 enable thepre-emphasis of the output signals DQ_A, DQ_B and DQ_C. To this end, thefirst to third variable emphasis drivers 602, 604 and 606 mayrespectively drive the first to third signal transmission lines 611, 631and 651 with various driving forces based on the transition informationof the first to third input signals DQ<0:2>. The first to third variableemphasis drivers 602, 604 and 606 may control the driving forcesaccording to the level changes of the first to third input signalsDQ<0:2>. The transmission device 6 may be an interface circuit capableof transmitting multilevel signals with a high level, a middle level anda low level, and the first to third input signals DQ<0:2> may each haveone level of the high level, the middle level and the low level. Thefirst variable emphasis driver 602 may additionally drive the firstsignal transmission line 611 when the first input signal DQ<0>transitions from any one level to another level. The first variableemphasis driver 602 may drive the first signal transmission line 611with a first driving force when the first input signal DQ<0> transitionsfrom the middle level to the high level, and may drive the first signaltransmission line 611 with a second driving force when the first inputsignal DQ<0> transitions from the low level to the high level. Thesecond driving force may be larger than the first driving force. Forinstance, the second driving force may be 2 times the first drivingforce. Similarly, the first variable emphasis driver 602 may drive thefirst signal transmission line 611 with the first driving force when thefirst input signal DQ<0> transitions from the middle level to the lowlevel, and may drive the first signal transmission line 611 with thesecond driving force when the first input signal DQ<0> transitions fromthe high level to the low level. Namely, the first variable emphasisdriver 602 may control a driving force for driving the first signaltransmission line 611 based on a voltage level difference by which thefirst input signal DQ<0> transitions. The first variable emphasis driver602 may drive the first signal transmission line 611 to a voltage levelcorresponding to the middle level when the first input signal DQ<0>retains the middle level or transitions from the high level or the lowlevel to the middle level.

Similarly to the first variable emphasis driver 602, the second andthird variable emphasis drivers 604 and 606 may control driving forcesfor driving the second and third signal transmission lines 631 and 651,respectively, based on voltage level differences by which the second andthird input signals DQ<1> and DQ<2> transition, respectively. The secondand third variable emphasis drivers 604 and 606 may drive the second andthird signal transmission lines 631 and 651 to a voltage levelcorresponding to the middle level when the second and third inputsignals DQ<1> and DQ<2> retain the middle level or transition from thehigh level or the low level to the middle level.

Referring to FIG. 6, the first variable emphasis driver 602 may includefirst and second pre-emphasis drivers 621 and 622. The first and secondpre-emphasis drivers 621 and 622 may drive the first signal transmissionline 611 to the power supply voltage or a ground voltage based on thetransition information of the first input signal DQ<0>. The first andsecond pre-emphasis drivers 621 and 622 may operate by receiving thepower supply voltage. The first and second pre-emphasis drivers 621 and622 may respectively have a driving force corresponding to the firstdriving force. The driving strength and magnitude of the first andsecond pre-emphasis drivers 621 and 622 may be smaller than the drivingstrength and magnitude of the first main driver 601. If the first inputsignal DQ<0> transitions from the middle level to the high level, anyone of the first and second pre-emphasis drivers 621 and 622 may beturned on and drive the first signal transmission line 611 to the levelof the power supply voltage. If the first input signal DQ<0> transitionsfrom the low level to the high level, both the first and secondpre-emphasis drivers 621 and 622 may be turned on and drive the firstsignal transmission line 611 to the level of the power supply voltage.If the first input signal DQ<0> transitions from the middle level to thelow level, any one of the first and second pre-emphasis drivers 621 and622 may be turned on and drive the first signal transmission line 611 tothe level of the ground voltage. If the first input signal DQ<0>transitions from the high level to the low level, both the first andsecond pre-emphasis drivers 621 and 622 may be turned on and drive thefirst signal transmission line 611 to the level of the ground voltage.When the first input signal DQ<0> retains the middle level ortransitions from the high level or the low level to the middle level,both the first and second pre-emphasis drivers 621 and 622 may be turnedon. In this example, any one of the first and second pre-emphasisdrivers 621 and 622 may drive the first signal transmission line 611 tothe level of the power supply voltage, and the other may drive the firstsignal transmission line 611 to the level of the ground voltage.

The second variable emphasis driver 604 may include third and fourthpre-emphasis drivers 641 and 642, and the third variable emphasis driver606 may include fifth and sixth pre-emphasis drivers 661 and 662. Thethird to sixth pre-emphasis drivers 641, 642, 661 and 662 may drive thesecond and third signal transmission lines 631 and 651 to the powersupply voltage or the ground voltage based on the transition informationof the second and third input signals DQ<1> and DQ<2>, respectively. Thethird to sixth pre-emphasis drivers 641, 642, 661 and 662 may operatesimilarly to the first and second pre-emphasis drivers 621 and 622.

The transmission device 6 may further include an output control unit670. The output control unit 670 may control the driving forces of thefirst to third main drivers 601, 603 and 605 and the first to thirdvariable emphasis drivers 602, 604 and 606 based on the first to thirdinput signals DQ<0:2>. The output control unit 670 may generate first tothird main driver control signals MCONA, MCONB and MCONC based on thefirst to third input signals DQ<0:2>. The first to third main drivers601, 603 and 605 may respectively drive the first to third signaltransmission lines 611, 631 and 651 to levels corresponding to the firstto third input signals DQ<0:2> in response to the first to third maindriver control signals MCONA, MCONB and MCONC. The output control unit670 may generate first to sixth pre-emphasis driver control signalsPCONA1, PCONA2, PCONB1, PCONB2, PCONC1 and PCONC2 based on thetransition information of the first to third input signals DQ<0:2>. Thefirst to sixth pre-emphasis driver control signals PCONA1, PCONA2,PCONB1, PCONB2, PCONC1 and PCONC2 may respectively have information onwhether to turn on the first to sixth pre-emphasis drivers 621, 622,641, 642, 661 and 662 and whether to perform pull-up or pull-downdriving. The output control unit 670 may determine whether the first tosixth pre-emphasis drivers 621, 622, 641, 642, 661 and 662 pull-up orpull-down drive the first to third signal transmission lines 611, 631and 651, based on voltage levels by which the first to third inputsignals DQ<0:2> transition. The output control unit 670 may generate thetransition information according to the level changes of the inputsignals DQ<0:2>. The output control unit 670 may generate the transitioninformation by comparing the levels of previously inputted input signalsDQ<0:2> and the levels of currently inputted input signals DQ<0:2>, andgenerate the first to sixth pre-emphasis driver control signals PCONA1,PCONA2, PCONB1, PCONB2, PCONC1 and PCONC2 based on the transitioninformation.

In the example where a variable emphasis driver includes at least 3pre-emphasis drivers, transmission of multilevel signals having at least4 levels is enabled. For example, when assuming that an output signalmay have a low level, a middle-low level, a middle-high level and a highlevel, a variable emphasis driver may include 3 pre-emphasis drivers. Ifan input signal transitions from a middle-high level to a high level, 1pre-emphasis driver may be turned on and drive a signal transmissionline to a power supply voltage, and if the input signal transitions froma middle-low level to the high level, 2 pre-emphasis drivers may beturned on and drive the signal transmission line to the power supplyvoltage. Further, if the input signal transitions from a low level tothe high level, all the 3 pre-emphasis drivers may be turned on anddrive the signal transmission line to the power supply voltage.Accordingly, a pre-emphasis strength may be variously changed accordingto a level by which the input signal transitions, and the transitiontime of the output signal outputted through the signal transmission linemay be variously controlled.

FIG. 7 is a representation of an example of a timing diagram to assistin the explanation of the operation of the transmission device 6illustrated in FIG. 6. Referring to FIG. 7, illustrated are a waveform Aof the first output signal DQ_A in the example where the first inputsignal DQ<0> transitions from the middle level to the high level and awaveform B of the first output signal DQ_A in the example where thefirst input signal DQ<0> transitions from the low level to the highlevel. In the example of the waveform A, any one of the first and secondpre-emphasis drivers 621 and 622 may be turned on, and the turned-on onepre-emphasis driver may drive the first signal transmission line 611 tothe level of the power supply voltage. As the first signal transmissionline 611 is driven to the high level by the first main driver 601 and isadditionally driven by the turned-on one pre-emphasis driver, the firstsignal transmission line 611 may easily reach the high level. In theexample of the waveform B, since the level change of the first inputsignal DQ<0> is larger than the case of the waveform A, both the firstand second pre-emphasis drivers 621 and 622 may be turned on and drivethe first signal transmission line 611 to the level of the power supplyvoltage. The variable emphasis driver 602 may drive the first signaltransmission line 611 with a first driving force in the example usedwith the waveform A, and may drive the first signal transmission line611 with a second driving force larger than the first driving force inthe example used with the waveform B. Accordingly, even when the firstinput signal DQ<0> transitions by a large voltage level difference, thefirst signal transmission line 611 may easily reach the high level. Inan embodiment, by controlling the driving force of the variable emphasisdriver 602, it may be possible to make a time at which the first signaltransmission line 611 transitions to the high level in the example ofthe waveform A and a time at which the first signal transmission line611 transitions to the high level in the case of the waveform B, thesame or substantially the same.

Referring to FIG. 7, there are illustrated a waveform C of the firstoutput signal DQ_A in the example where the first input signal DQ<0>transitions from the middle level to the low level and a waveform D ofthe first output signal DQ_A in the example where the first input signalDQ<0> transitions from the high level to the low level. In the exampleof the waveform C, any one of the first and second pre-emphasis drivers621 and 622 may be turned on, and the turned-on one pre-emphasis drivermay drive the first signal transmission line 611 to the level of theground voltage. As the first signal transmission line 611 is driven tothe low level by the first main driver 601 and is additionally driven bythe turned-on one pre-emphasis driver, the first signal transmissionline 611 may easily reach the low level. In the example of the waveformD, since the level change of the first input signal DQ<0> is larger thanthe example of the waveform C, both the first and second pre-emphasisdrivers 621 and 622 may be turned on and may drive the first signaltransmission line 611 to the level of the ground voltage. The variableemphasis driver 602 may drive the first signal transmission line 611with the first driving force in the example used with the waveform C,and may drive the first signal transmission line 611 with the seconddriving force larger than the first driving force in the example usedwith the waveform D. Accordingly, even when the first input signal DQ<0>transitions by a large voltage level difference, the first signaltransmission line 611 may easily reach the low level.

In the embodiments, since the pre-emphasis strength of an output signalto be transmitted through a signal transmission line is controlled in avariety of ways according to the transition information of an inputsignal, a signal may be precisely transmitted, and the data eye orwindow of the signal to be transmitted through the signal transmissionline may be sufficiently secured.

While various embodiments have been described above, it will beunderstood to those skilled in the art that the embodiments describedare examples only. Accordingly, the interface circuit for high speedcommunication and the system including the same described herein shouldnot be limited based on the described embodiments.

What is claimed is:
 1. A transmission device comprising: a main driverconfigured to drive an output node based on an input signal, andgenerate an output signal with multiple levels; and a variable emphasisdriver configured to drive the output node with various driving forcesbased on transition information of the input signal.
 2. The transmissiondevice according to claim 1, wherein the variable emphasis driverchanges a strength for driving the output node, according to a voltagelevel change of the input signal.
 3. The transmission device accordingto claim 1, wherein the variable emphasis driver increases the strengthfor driving the output node, as a change in a voltage level of the inputsignal increases.
 4. The transmission device according to claim 1,wherein the multiple levels include a high level, a middle level and alow level, the high level has a potential higher than the middle level,and the middle level has a potential higher than the low level.
 5. Thetransmission device according to claim 1, wherein the input signaltransitions from one level to a plurality of different levels, andwherein, when the input signal transitions from any one level to anadjacent level, the variable emphasis driver drives the output node witha predetermined strength, and, when the input signal transitions fromthe any one level to a level exceeding the adjacent level, the variableemphasis driver drives the output node with a strength larger than thepredetermined strength in proportion to the level exceeding the adjacentlevel.
 6. The transmission device according to claim 1, furthercomprising: an output control unit configured to control a driving forceof the main driver and a driving force of the variable emphasis driverbased on the input signal.
 7. The transmission device according to claim1, wherein the variable emphasis driver drives the output node until avoltage level of the output node transitions from any one level toanother level.
 8. The transmission device according to claim 1, whereinthe variable emphasis driver drives the output node to a power supplyvoltage or a ground voltage based on the transmission information of theinput signal.
 9. The transmission device according to claim 1, wherein adriving strength and magnitude applied to the output node by thevariable emphasis driver is less than a driving strength and magnitudeapplied to the output node by the main driver.
 10. The transmissiondevice according to claim 1, wherein the variable emphasis drivercomprises a plurality of pre-emphasis drivers, and wherein the variableemphasis driver increases the strength for driving by using a greaternumber of pre-emphasis drivers to drive the output node.
 11. Atransmission device comprising: a main driver configured to output anoutput signal with one level among a high level, a middle level and alow level, to an output node, based on an input signal; and a variableemphasis driver configured to drive the output node with one of firstand second driving forces based on transition information of the inputsignal.
 12. The transmission device according to claim 11, wherein thehigh level has a potential higher by a unit level than the middle level,and the middle level has a potential higher by the unit level than thelow level.
 13. The transmission device according to claim 12, whereinthe second driving force is larger than the first driving force, andwherein the variable emphasis driver drives the output node with thefirst driving force when the input signal transitions from any one levelby one unit level, and drives the output node with the second drivingforce when the input signal transitions by two unit levels.
 14. Thetransmission device according to claim 11, wherein the variable emphasisdriver drives the output node to a voltage level corresponding to themiddle level when the input signal does not transition from the middlelevel.
 15. The transmission device according to claim 11, wherein thevariable emphasis driver drives the output node to a voltage levelcorresponding to the middle level when the input signal transitions fromthe low level or the high level to the middle level.
 16. Thetransmission device according to claim 11, wherein the variable emphasisdriver comprises: a first pre-emphasis driver configured to drive theoutput node to one of a power supply voltage and a ground voltageaccording to the transition information of the input signal; and asecond pre-emphasis driver configured to drive the output node to one ofthe power supply voltage and the ground voltage according to thetransition information of the input signal.
 17. The transmission deviceaccording to claim 16, wherein one of the first and second pre-emphasisdrivers drives the output node to a level of the power supply voltagewhen the input signal transitions from the middle level to the highlevel, and both the first and second pre-emphasis drivers drive theoutput node to the level of the power supply voltage when the inputsignal transitions from the low level to the high level.
 18. Thetransmission device according to claim 16, wherein one of the first andsecond pre-emphasis drivers drives the output node to a level of theground voltage when the input signal transitions from the middle levelto the low level, and both the first and second pre-emphasis driversdrive the output node to the level of the ground voltage when the inputsignal transitions from the high level to the low level.
 19. Thetransmission device according to claim 16, wherein, when the inputsignal transitions to the middle level, one of the first and secondpre-emphasis drivers drives the output node to the level of the powersupply voltage, and the other drives the output node to the level of theground voltage.
 20. The transmission device according to claim 11,wherein the variable emphasis driver drives the output node until avoltage level of the output node transitions from any one level toanother level.
 21. The transmission device according to claim 11,further comprising: an output control unit configured to control adriving force of the main driver and a driving force of the variableemphasis driver based on the input signal.
 22. The transmission deviceaccording to claim 21, wherein the output control unit generates thetransition information by comparing a previously inputted input signaland a currently inputted input signal.
 23. The transmission deviceaccording to claim 11, wherein the high level has 3/4 of a voltagelevel, the middle level has 2/4 of the voltage level, and the low levelhas 1/4 of the voltage level.
 24. A transmission device comprising: avariable emphasis driver configured to change a pre-emphasis strengthaccording to a level by which an input signal transitions to control atransition time of an output signal.
 25. The transmission deviceaccording to claim 23, wherein the variable emphasis driver comprises aplurality of pre-emphasis drivers, and wherein the variable emphasisdriver increases the strength for driving by using a greater number ofpre-emphasis drivers.
 26. The transmission device according to claim 24,wherein the variable emphasis driver increases the strength for drivingthe output node, as a change in a voltage level of the input signalincreases.